Patent GB-1157494-A (GB)
Title: Improvements in or relating to Pre-Stressing of Concrete Pressure Vessels.
Inventor: TAYLOR REGINALD SIDNEY
IPC: E04G21/12
Filed: 1966-08-12
Abstract: 1,157,494. Winding wire around a concrete structure. TAYLOR WOODROW CONSTRUCTION Ltd. 9 Aug., 1967 [12 Aug., 1966], No. 36324/66. Heading B3E. Apparatus for winding pre-stressing wire around an upstanding cylindrical vessel comprises a platform adapted to surround the vessel and movable vertically relatively thereto, means for positively locating the platform in any selected vertical position and a mobile unit supported on the platform for movement around the vessel, and equipped with a wire supply holding means and with tensioning means through which wire from the holding means will be drawn, so that with the platform at a selected position and an end of the wire drawn from the holding means via the tensioning means securely anchored to the vessel, movement of the unit therearound will result in winding of the wire around the vessel at a predetermined tension.The concrete pressure vessel 10 has circumferential ribs forming between them grooves into which the wire is wound. The annular platform 11 surrounds the structure and is suspended by cables 12 which pass over the pulleys at the upper ends of columns 13 arranged in a circle around the structure. The cables are attached in pairs to sheaves, each sheave being connected by a single hoist rope and a multiple sheave system to a winch operated by an electric motor, the motors being synchronized, so that the platform remains horizontal as it is moved. The platform is locked at a desired height by bolts 19 which are moved out to engage blocks 18 on the columns 13, and by lugs 24 on pivoted levers 20 which are moved by hydraulic jacks 23 to engage an appropriate rib on the structure. Mounted on the platform 11 are circular I- beams 27 which support rails on which the wirecarrying train runs on load-bearing wheels 32 and lateral guide wheels 33. A fixed chain 28 passes round the inner beam 27. The wire carrying train comprises a leading trolley 30 carrying an hydraulic power unit 34 which drives a sprocket 35, around which the chain 28 passes. The chain also passes round tensioning sprockets 36, 37, 38. The wire W is drawn from a storage spool on the rear trolley 31, through a wire tensioning unit 40 and passes over a sheave 39 which guides it on to the structure. The tensioning device 40 comprises two opposed endless belts (41, 42), Fig. 5 (not shown), carrying friction pads which engage the wire. The belt assemblies are drawn together to grip the wire by hydraulic cylinders. The lower part of the tensioning device is mounted for floating movement parallel to the wire. If the wire tension varies the lower part of the tensioning device moves against load cells which control the speed of hydraulic motors, driving sprockets over which the belts are entrained, so that the speed differential between the belts and the trolleys is maintained. The sheave 39 is mounted so that it can be tilted, one side of the pulley remaining in alignment with the wire emerging from the tensioning unit and the other side of the pulley being raised or lowered by an amount corresponding to the thickness of the wire so that successive turns do not overlap. The Specification states that the tension unit may be replaced by a linear induction motor and that the hoisting cables may be replaced by hydraulic jacks connected between the platform and a second underlying platform, both the platforms being capable of being locked to the vessel, so that a self-climbing unit is provided. Alternatively, upper and lower platforms, each supported by hoist ropes and carrying a wirewinding train can be provided. In a further construction the platform carrying the track is suspended from the top of the structure.